Prolonged elevation of insulin content in the unicellular tetrahymena after insulin treatment: Induction of insulin production or storage?

In the unicellular organism, Tetrahymena, the first encounter with an exoge neously given hormone results in hormonal imprinting. This causes an increa se of the binding capacity of receptors and the production of the appropria te hormone in the progeny generations of the treated cell. In the present e xperiments the quantity (using radioimmunoassay) and localization (using co nfocal laser scanning microscopy) of the immunologically insulin-like mater ial (hereafter insulin) were studied for 10 days after 4 h or 24 h 10(-6) M insulin treatment (hormonal imprinting). Forty-eight hours after both insu lin treatments a high quantity of insulin was present in the cells. This va lue was also significantly increased after 96 h. After 8 days the differenc e to the control was significant only in the 24 h treated group. Confocal m icroscopy (using antibody to pig insulin) localized insulin in the cell bod y. The oral field contained extremely high quantities of the endogeneous ho rmone. Insulin treatment (after 48 and 96 h) caused an elevation of insulin content in general, and specific accumulation in the posterior sections of the cell, around the nucleus and in the periphery were observed. Ten days after both treatments only the peripheral region of the cell body and the c iliary row contained more insulin than the control. This means that after i nsulin treatment the quantity of insulin increases for a lengthy time perio d which is followed by the expression of insulin in the peripheral region. Insulin contained by Tetrahymena 48 h after imprinting stimulated glucose u ptake of rat diaphragm. Copyright (C) 1999 John Wiley & Sons, Ltd.